PORTSMOUTH, N.H. -- A great transformation is occurring. You can see it, you can smell it, you can feel it and, if you take a sip of the sweet liquor of the season, this state's fabled apple cider, you can taste it. There's a bite in the air, matching the crispness of the autumn apples. There are patches of red and orange amid the maples and oaks on the hillsides. Before long there will be a rime of ice on the ponds.

But the season isn't the only thing that's changing.

This month brings a discernible turn in the struggle for the White House that is a preoccupation in this state, site of the first presidential primary. It will be apparent in Tuesday night's debate among the Democratic candidates. But it's also apparent in the tone and timbre of the race. It's turning serious, to be sure. But it's also turning from merely a chase to gain office to a question of governing.

And it is turning, at least for the moment, away from New Hampshire, which holds its primary Feb. 9, and Iowa, which holds its precinct caucuses a mere eight days earlier. The candidates are still streaming here  nearly 10 of them, from both parties, are planning to attend the No Labels National Problem Solving Convention in Manchester on Monday, with many of them returning here for the New Hampshire Housing Summit at St. Anselm College Friday  but the attention is shifting, if only for a time, to Washington.

And the attention is shifting to real problems requiring real solutions and demanding actual political decisions. There's a difference between talking in Manchester about housing and casting votes in the House in Washington.

Last week the first round of wrangling to succeed John Boehner as speaker of the House occurred, and it was as much spectacle as selection, underlining the deep fissures within the GOP  fissures that are reflected here on the campaign trail. The 2016 presidential race is about choosing a leader to govern a country whose governing class seems incapable of the task. That's why amateurs  the word is not necessarily disparaging, though it applies to some of them  are in the lead here and elsewhere.

And last week the negotiations for the Trans Pacific Partnership (TPP) concluded, signaling the beginning of a titanic struggle in the capital (and on the campaign trail) over trade issues. For months the words "protectionist" and "job losses" have been tossed across the political landscape, mostly by candidates looking for advantage rather than searching for understanding. That phase of the trade debate has now officially ended.

So have many of the assumptions that sat beneath the facile debate on the TPP. On the campaign trail, especially among Democrats, it was a good bet that there would be sufficient environmental risks that it would be safe for White House aspirants to oppose the measure, affecting a dozen nations, on that basis. But leading environmental groups, citing protections against overfishing and illegal trade in certain plants and animals, have said the pact is not only acceptable but also a major step forward.

No such conclusion is expected from organized labor, which is very likely why Hillary Rodham Clinton, who as secretary of state, and in her later memoir, praised the measure, came out last week against it  a sure boon to her in states with strong union elements (such as Iowa, with its United Auto Workers presence).

But Democratic presidential candidates aren't the only ones facing choices on the trade agreement.

Nearly a century ago Republicans could be counted on to support trade barriers; nearly 15 times as many House Republicans as Democrats voted for the Smoot-Hawley tariff in 1930. Now the supporters of trade barriers are on the Democratic side  it's been that way for almost three decades  while contemporary Republicans are split between those who support free trade (because of its congruity with open markets) and those, including billionaire businessman Donald Trump, skeptical of anything produced by the Obama administration.

Trade issues are the sort of political topics that put politicians asleep  until they keep them up at night.

Like so much of economics, trade issues are in part philosophical, pitting unfettered business activity against government intervention. When there's no actual proposal on the table, politicians and professors love these sorts of issues. They can take brave views, buttressing them by devout belief in the magic of the marketplace or the indispensability of government.

That was for last month. This month there's an actual proposal to confront, and things are a lot more complicated.

The debate comes down mostly to jobs and growth. The Democrats want to protect jobs, mostly through governmental action, and the Republicans to spawn jobs, mostly through growth. That's an oversimplification, of course, and there's plenty of wiggle room in both parties' positions. But that collision is imperiling the trade pact, which (and here is another reason why it's such a volatile issue) is very likely the last big priority of President Barack Obama.

The Obama factor has its own dynamic. Republicans who otherwise might favor the TPP may posture against it just to hurt the president. Democrats who otherwise might support the pact (Ms. Clinton especially) might lean in opposition to show that they are not clones of the president. No one ever said good posture was a prerequisite for politics.

Now, back to the struggle to succeed Mr. Boehner. In that tumultuous process, the Republican majority must choose between regular order  a legislative phrase that means the customary, accepted way of doing things  and rebellion. Sometimes the regular order is a good thing, and sometimes rebellion is a good thing. (It was the founding Democrat, Thomas Jefferson, whose remarks on rebellion almost certainly will be in the air all month.) But the GOP can't have it both ways. It must choose. And the presidential candidates here and in Iowa must react to that choice.

Overall, this change in the season is a positive for all concerned, except perhaps for the poor souls running for president. It underlines what this presidential race is all about  making choices. John F. Kennedy liked to say that to govern was to choose. This time around, the politicians who want to govern first have to choose. Bad for them.

Good for us.

David Shribman, a Pulitzer Prize winner in journalism, is executive editor of the Pittsburgh Post-Gazette.